101
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Chuang CHM, Brown PR, Bulović V, Bawendi MG. Improved performance and stability in quantum dot solar cells through band alignment engineering. Nat Mater 2014; 13:796-801. [PMID: 24859641 PMCID: PMC4110173 DOI: 10.1038/nmat3984] [Citation(s) in RCA: 644] [Impact Index Per Article: 64.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 04/15/2014] [Indexed: 05/19/2023]
Abstract
Solution processing is a promising route for the realization of low-cost, large-area, flexible and lightweight photovoltaic devices with short energy payback time and high specific power. However, solar cells based on solution-processed organic, inorganic and hybrid materials reported thus far generally suffer from poor air stability, require an inert-atmosphere processing environment or necessitate high-temperature processing, all of which increase manufacturing complexities and costs. Simultaneously fulfilling the goals of high efficiency, low-temperature fabrication conditions and good atmospheric stability remains a major technical challenge, which may be addressed, as we demonstrate here, with the development of room-temperature solution-processed ZnO/PbS quantum dot solar cells. By engineering the band alignment of the quantum dot layers through the use of different ligand treatments, a certified efficiency of 8.55% has been reached. Furthermore, the performance of unencapsulated devices remains unchanged for over 150 days of storage in air. This material system introduces a new approach towards the goal of high-performance air-stable solar cells compatible with simple solution processes and deposition on flexible substrates.
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Affiliation(s)
- Chia-Hao M. Chuang
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Patrick R. Brown
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Vladimir Bulović
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
- Correspondence and requests for materials should be addressed to M.G.B. ()
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102
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Ko DK, Brown PR, Bawendi MG, Bulović V. p-i-n Heterojunction solar cells with a colloidal quantum-dot absorber layer. Adv Mater 2014; 26:4845-50. [PMID: 24862978 DOI: 10.1002/adma.201401250] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 04/15/2014] [Indexed: 05/04/2023]
Abstract
A quantum-dot (QD) p-i-n heterojunction solar cell with an increased depletion region is demonstrated by depleting the QD layer from both the front and back junctions. Due to a combination of improved charged extraction and increased light absorption, a 120% increase in the short-circuit current is achieved compared with that of conventional ZnO/QD devices.
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Affiliation(s)
- Dong-Kyun Ko
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
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103
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Coropceanu I, Bawendi MG. Core/shell quantum dot based luminescent solar concentrators with reduced reabsorption and enhanced efficiency. Nano Lett 2014; 14:4097-101. [PMID: 24902615 DOI: 10.1021/nl501627e] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
CdSe/CdS core/shell quantum dots (QDs) have been optimized toward luminescent solar concentration (LSC) applications. Systematically increasing the shell thickness continuously reduced reabsorption up to a factor of 45 for the thickest QDs studied (with ca. 14 monolayers of CdS) compared to the initial CdSe cores. Moreover, an improved synthetic method was developed that retains a high-fluorescence quantum yield, even for particles with the thickest shell volume, for which a quantum yield of 86% was measured in solution. These high quantum yield thick shell quantum dots were embedded in a polymer matrix, yielding highly transparent composites to serve as prototype LSCs, which exhibited an optical efficiency as high as 48%. A Monte Carlo simulation was developed to model LSC performance and to identify the major loss channels for LSCs incorporating the materials developed. The results of the simulation are in excellent agreement with the experimental data.
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Affiliation(s)
- Igor Coropceanu
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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104
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Brown PR, Kim D, Lunt RR, Zhao N, Bawendi MG, Grossman JC, Bulović V. Energy level modification in lead sulfide quantum dot thin films through ligand exchange. ACS Nano 2014; 8:5863-72. [PMID: 24824726 DOI: 10.1021/nn500897c] [Citation(s) in RCA: 399] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The electronic properties of colloidal quantum dots (QDs) are critically dependent on both QD size and surface chemistry. Modification of quantum confinement provides control of the QD bandgap, while ligand-induced surface dipoles present a hitherto underutilized means of control over the absolute energy levels of QDs within electronic devices. Here, we show that the energy levels of lead sulfide QDs, measured by ultraviolet photoelectron spectroscopy, shift by up to 0.9 eV between different chemical ligand treatments. The directions of these energy shifts match the results of atomistic density functional theory simulations and scale with the ligand dipole moment. Trends in the performance of photovoltaic devices employing ligand-modified QD films are consistent with the measured energy level shifts. These results identify surface-chemistry-mediated energy level shifts as a means of predictably controlling the electronic properties of colloidal QD films and as a versatile adjustable parameter in the performance optimization of QD optoelectronic devices.
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Affiliation(s)
- Patrick R Brown
- Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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105
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Yuen-Zhou J, Arias DH, Eisele DM, Steiner CP, Krich JJ, Bawendi MG, Nelson KA, Aspuru-Guzik A. Coherent exciton dynamics in supramolecular light-harvesting nanotubes revealed by ultrafast quantum process tomography. ACS Nano 2014; 8:5527-34. [PMID: 24724614 DOI: 10.1021/nn406107q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Long-lived exciton coherences have been recently observed in photosynthetic complexes via ultrafast spectroscopy, opening exciting possibilities for the study and design of coherent exciton transport. Yet, ambiguity in the spectroscopic signals has led to arguments against interpreting them in terms of exciton dynamics, demanding more stringent tests. We propose a novel strategy, quantum process tomography (QPT), for ultrafast spectroscopy and apply it to reconstruct the evolving quantum state of excitons in double-walled supramolecular light-harvesting nanotubes at room temperature from eight narrowband transient grating experiments. Our analysis reveals the absence of nonsecular processes, unidirectional energy transfer from the outer to the inner wall exciton states, and coherence between those states lasting about 150 fs, indicating weak electronic coupling between the walls. Our work constitutes the first experimental QPT in a "warm" and complex system and provides an elegant scheme to maximize information from ultrafast spectroscopy experiments.
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Affiliation(s)
- Joel Yuen-Zhou
- Center for Excitonics, Research Laboratory of Electronics, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States
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106
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Yost SR, Lee J, Wilson MWB, Wu T, McMahon DP, Parkhurst RR, Thompson NJ, Congreve DN, Rao A, Johnson K, Sfeir MY, Bawendi MG, Swager TM, Friend RH, Baldo MA, Van Voorhis T. A transferable model for singlet-fission kinetics. Nat Chem 2014; 6:492-7. [DOI: 10.1038/nchem.1945] [Citation(s) in RCA: 359] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 04/04/2014] [Indexed: 01/28/2023]
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107
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Lemon CM, Curtin PN, Somers RC, Greytak AB, Lanning RM, Jain RK, Bawendi MG, Nocera DG. Metabolic tumor profiling with pH, oxygen, and glucose chemosensors on a quantum dot scaffold. Inorg Chem 2014; 53:1900-15. [PMID: 24143874 PMCID: PMC3944830 DOI: 10.1021/ic401587r] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Acidity, hypoxia, and glucose levels characterize the tumor microenvironment rendering pH, pO2, and pGlucose, respectively, important indicators of tumor health. To this end, understanding how these parameters change can be a powerful tool for the development of novel and effective therapeutics. We have designed optical chemosensors that feature a quantum dot and an analyte-responsive dye. These noninvasive chemosensors permit pH, oxygen, and glucose to be monitored dynamically within the tumor microenvironment by using multiphoton imaging.
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Affiliation(s)
- Christopher M. Lemon
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138
| | - Peter N. Curtin
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Rebecca C. Somers
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Andrew B. Greytak
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208
| | - Ryan M. Lanning
- Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, MA 02114
| | - Rakesh K. Jain
- Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, MA 02114
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138
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108
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Cui J, Beyler AP, Bischof TS, Wilson MWB, Bawendi MG. Deconstructing the photon stream from single nanocrystals: from binning to correlation. Chem Soc Rev 2014; 43:1287-310. [DOI: 10.1039/c3cs60330j] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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109
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Beyler AP, Marshall LF, Cui J, Brokmann X, Bawendi MG. Direct observation of rapid discrete spectral dynamics in single colloidal CdSe-CdS core-shell quantum dots. Phys Rev Lett 2013; 111:177401. [PMID: 24206518 DOI: 10.1103/physrevlett.111.177401] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Indexed: 05/23/2023]
Abstract
We measure the anomalous spectral diffusion of single colloidal quantum dots over eight temporal decades simultaneously by combining single-molecule spectroscopy and photon-correlation Fourier spectroscopy. Our technique distinguishes between discrete and continuous dynamics and directly reveals that the quasicontinuous spectral diffusion observed using conventional spectroscopy is composed of rapid, discrete spectral jumps. Despite their multiple time scales, these dynamics can be captured by a single mechanism whose parameters vary widely between dots and over time in individual dots.
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Affiliation(s)
- Andrew P Beyler
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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110
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Abstract
Supramolecular assemblies of a quantum dot (QD) associated to palladium(II) porphyrins have been developed to detect oxygen (pO2) in organic solvents. Palladium porphyrins are sensitive in the 0-160 Torr range, making them ideal phosphors for in vivo biological oxygen quantification. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self-assembled nanosensors. Appreciable overlap between QD emission and porphyrin absorption features results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. The QD serves as a photon antenna, enhancing porphyrin emission under both one- and two-photon excitation, demonstrating that QD-palladium porphyrin conjugates may be used for oxygen sensing over physiological oxygen ranges.
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Affiliation(s)
- Christopher M Lemon
- Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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111
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Cui J, Beyler AP, Marshall LF, Chen O, Harris DK, Wanger DD, Brokmann X, Bawendi MG. Direct probe of spectral inhomogeneity reveals synthetic tunability of single-nanocrystal spectral linewidths. Nat Chem 2013; 5:602-6. [PMID: 23787751 DOI: 10.1038/nchem.1654] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 04/16/2013] [Indexed: 11/09/2022]
Abstract
The spectral linewidth of an ensemble of fluorescent emitters is dictated by the combination of single-emitter linewidths and sample inhomogeneity. For semiconductor nanocrystals, efforts to tune ensemble linewidths for optical applications have focused primarily on eliminating sample inhomogeneities, because conventional single-molecule methods cannot reliably build accurate ensemble-level statistics for single-particle linewidths. Photon-correlation Fourier spectroscopy in solution (S-PCFS) offers a unique approach to investigating single-nanocrystal spectra with large sample statistics and high signal-to-noise ratios, without user selection bias and at fast timescales. With S-PCFS, we directly and quantitatively deconstruct the ensemble linewidth into contributions from the average single-particle linewidth and from sample inhomogeneity. We demonstrate that single-particle linewidths vary significantly from batch to batch and can be synthetically controlled. These findings delineate the synthetic challenges facing underdeveloped nanomaterials such as InP and InAs core-shell particles and introduce new avenues for the synthetic optimization of fluorescent nanoparticles.
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Affiliation(s)
- Jian Cui
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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112
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Jean J, Chang S, Brown PR, Cheng JJ, Rekemeyer PH, Bawendi MG, Gradečak S, Bulović V. ZnO nanowire arrays for enhanced photocurrent in PbS quantum dot solar cells. Adv Mater 2013; 25:2790-6. [PMID: 23440957 DOI: 10.1002/adma.201204192] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 11/24/2012] [Indexed: 05/11/2023]
Abstract
Vertical arrays of ZnO nanowires can decouple light absorption from carrier collection in PbS quantum dot solar cells and increase power conversion efficiencies by 35%. The resulting ordered bulk heterojunction devices achieve short-circuit current densities in excess of 20 mA cm(-2) and efficiencies of up to 4.9%.
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Affiliation(s)
- Joel Jean
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
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113
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Chen O, Zhao J, Chauhan VP, Cui J, Wong C, Harris DK, Wei H, Han HS, Fukumura D, Jain RK, Bawendi MG. Compact high-quality CdSe-CdS core-shell nanocrystals with narrow emission linewidths and suppressed blinking. Nat Mater 2013; 12:445-51. [PMID: 23377294 PMCID: PMC3677691 DOI: 10.1038/nmat3539] [Citation(s) in RCA: 642] [Impact Index Per Article: 58.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 12/04/2012] [Indexed: 05/17/2023]
Abstract
High particle uniformity, high photoluminescence quantum yields, narrow and symmetric emission spectral lineshapes and minimal single-dot emission intermittency (known as blinking) have been recognized as universal requirements for the successful use of colloidal quantum dots in nearly all optical applications. However, synthesizing samples that simultaneously meet all these four criteria has proven challenging. Here, we report the synthesis of such high-quality CdSe-CdS core-shell quantum dots in an optimized process that maintains a slow growth rate of the shell through the use of octanethiol and cadmium oleate as precursors. In contrast with previous observations, single-dot blinking is significantly suppressed with only a relatively thin shell. Furthermore, we demonstrate the elimination of the ensemble luminescence photodarkening that is an intrinsic consequence of quantum dot blinking statistical ageing. Furthermore, the small size and high photoluminescence quantum yields of these novel quantum dots render them superior in vivo imaging agents compared with conventional quantum dots. We anticipate these quantum dots will also result in significant improvement in the performance of quantum dots in other applications such as solid-state lighting and illumination.
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Affiliation(s)
- Ou Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Jing Zhao
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Vikash P. Chauhan
- Massachusetts General Hospital and Harvard Medical School, 100 Blossom St., Boston, MA 02114 (USA)
| | - Jian Cui
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Cliff Wong
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Daniel K. Harris
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - He Wei
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Hee-Sun Han
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
| | - Dai Fukumura
- Massachusetts General Hospital and Harvard Medical School, 100 Blossom St., Boston, MA 02114 (USA)
| | - Rakesh K. Jain
- Massachusetts General Hospital and Harvard Medical School, 100 Blossom St., Boston, MA 02114 (USA)
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (USA)
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114
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Manfrinato VR, Wanger DD, Strasfeld DB, Han HS, Marsili F, Arrieta JP, Mentzel TS, Bawendi MG, Berggren KK. Controlled placement of colloidal quantum dots in sub-15 nm clusters. Nanotechnology 2013; 24:125302. [PMID: 23466608 DOI: 10.1088/0957-4484/24/12/125302] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrated a technique to control the placement of 6 nm-diameter CdSe and 5 nm-diameter CdSe/CdZnS colloidal quantum dots (QDs) through electron-beam lithography. This QD-placement technique resulted in an average of three QDs in each cluster, and 87% of the templated sites were occupied by at least one QD. These QD clusters could be in close proximity to one another, with a minimum separation of 12 nm. Photoluminescence measurements of the fabricated QD clusters showed intermittent photoluminescence, which indicates that the QDs were optically active after the fabrication process. This optimized top-down lithographic process is a step towards the integration of individual QDs in optoelectronic and nano-optical systems.
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Affiliation(s)
- Vitor R Manfrinato
- Electrical Engineering and Computer Science Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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115
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Chang LY, Lunt RR, Brown PR, Bulović V, Bawendi MG. Low-temperature solution-processed solar cells based on PbS colloidal quantum dot/CdS heterojunctions. Nano Lett 2013; 13:994-9. [PMID: 23406331 DOI: 10.1021/nl3041417] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
PbS colloidal quantum dot heterojunction solar cells have shown significant improvements in performance, mostly based on devices that use high-temperature annealed transition metal oxides to create rectifying junctions with quantum dot thin films. Here, we demonstrate a solar cell based on the heterojunction formed between PbS colloidal quantum dot layers and CdS thin films that are deposited via a solution process at 80 °C. The resultant device, employing a 1,2-ethanedithiol ligand exchange scheme, exhibits an average power conversion efficiency of 3.5%. Through a combination of thickness-dependent current density-voltage characteristics, optical modeling, and capacitance measurements, the combined diffusion length and depletion width in the PbS quantum dot layer is found to be approximately 170 nm.
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Affiliation(s)
- Liang-Yi Chang
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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116
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Kay ER, Lee J, Nocera DG, Bawendi MG. Conformational control of energy transfer: a mechanism for biocompatible nanocrystal-based sensors. Angew Chem Int Ed Engl 2013; 52:1165-9. [PMID: 23225635 PMCID: PMC3793206 DOI: 10.1002/anie.201207181] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Indexed: 11/06/2022]
Abstract
Fold-up fluorophore : A new paradigm for designing self-referencing fluorescent nanosensors is demonstrated by interfacing a pH-triggered molecular conformational switch with quantum dots. Analytedependent, large-amplitude conformational motion controls the distance between the nanocrystal energy donor and an organic FRET acceptor. The result is a fluorescence signal capable of reporting pH values from individual endosomes in living cells.
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Affiliation(s)
| | | | - Daniel G. Nocera
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139-4307 (USA)
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139-4307 (USA)
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117
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Chauhan VP, Martin JD, Liu H, Lacorre DA, Jain SR, Kozin SV, Stylianopoulos T, Mousa AS, Han X, Adstamongkonkul P, Popović Z, Huang P, Bawendi MG, Boucher Y, Jain RK. Angiotensin inhibition enhances drug delivery and potentiates chemotherapy by decompressing tumour blood vessels. Nat Commun 2013; 4:2516. [PMID: 24084631 PMCID: PMC3806395 DOI: 10.1038/ncomms3516] [Citation(s) in RCA: 703] [Impact Index Per Article: 63.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 08/29/2013] [Indexed: 02/06/2023] Open
Abstract
Cancer and stromal cells actively exert physical forces (solid stress) to compress tumour blood vessels, thus reducing vascular perfusion. Tumour interstitial matrix also contributes to solid stress, with hyaluronan implicated as the primary matrix molecule responsible for vessel compression because of its swelling behaviour. Here we show, unexpectedly, that hyaluronan compresses vessels only in collagen-rich tumours, suggesting that collagen and hyaluronan together are critical targets for decompressing tumour vessels. We demonstrate that the angiotensin inhibitor losartan reduces stromal collagen and hyaluronan production, associated with decreased expression of profibrotic signals TGF-β1, CCN2 and ET-1, downstream of angiotensin-II-receptor-1 inhibition. Consequently, losartan reduces solid stress in tumours resulting in increased vascular perfusion. Through this physical mechanism, losartan improves drug and oxygen delivery to tumours, thereby potentiating chemotherapy and reducing hypoxia in breast and pancreatic cancer models. Thus, angiotensin inhibitors -inexpensive drugs with decades of safe use - could be rapidly repurposed as cancer therapeutics.
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MESH Headings
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensins/antagonists & inhibitors
- Angiotensins/metabolism
- Animals
- Antineoplastic Agents/pharmacology
- Cell Hypoxia
- Collagen/metabolism
- Connective Tissue Growth Factor/genetics
- Connective Tissue Growth Factor/metabolism
- Drug Repositioning
- Drug Synergism
- Endothelin-1/genetics
- Endothelin-1/metabolism
- Female
- Fluorouracil/pharmacology
- Gene Expression Regulation, Neoplastic
- Humans
- Hyaluronic Acid/metabolism
- Losartan/pharmacology
- Mammary Neoplasms, Experimental/blood supply
- Mammary Neoplasms, Experimental/drug therapy
- Mammary Neoplasms, Experimental/pathology
- Mechanotransduction, Cellular
- Mice
- Pancreatic Neoplasms/blood supply
- Pancreatic Neoplasms/drug therapy
- Pancreatic Neoplasms/pathology
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Stress, Mechanical
- Stromal Cells/drug effects
- Stromal Cells/metabolism
- Stromal Cells/pathology
- Transforming Growth Factor beta1/genetics
- Transforming Growth Factor beta1/metabolism
- Pancreatic Neoplasms
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Affiliation(s)
- Vikash P. Chauhan
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- These authors contributed equally to this work
| | - John D. Martin
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- These authors contributed equally to this work
| | - Hao Liu
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Delphine A. Lacorre
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Saloni R. Jain
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Sergey V. Kozin
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Triantafyllos Stylianopoulos
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- Department of Mechanical and Manufacturing Engineering, University of Cyprus CY-1678, Nicosia, Cyprus
| | - Ahmed S. Mousa
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Xiaoxing Han
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Pichet Adstamongkonkul
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Zoran Popović
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Peigen Huang
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Yves Boucher
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Rakesh K. Jain
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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118
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Wanger DD, Correa RE, Dauler EA, Bawendi MG. The dominant role of exciton quenching in PbS quantum-dot-based photovoltaic devices. Nano Lett 2013; 13:5907-12. [PMID: 24256125 DOI: 10.1021/nl402886j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We present a quantitative measurement of the number of trapped carriers combined with a measurement of exciton quenching to assess limiting mechanisms for current losses in PbS-quantum-dot-based photovoltaic devices. We use photocurrent intensity dependence and short-wave infrared transient photoluminescence and correlate these with device performance. We find that the effective density of trapped carriers ranges from 1 in 10 to 1 in 10,000 quantum dots, depending on ligand treatment, and that nonradiative exciton quenching, as opposed to recombination with trapped carriers, is likely the limiting mechanism in these devices.
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Affiliation(s)
- Darcy D Wanger
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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119
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Abstract
We have recently developed compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand coated superparamagnetic iron oxide nanoparticles (SPIONs) for use in various biomedical applications. The defining characteristics of ZDS-coated SPIONs are small hydrodynamic diameters, low non-specific interactions with fetal bovine serum, the opportunity for specific labeling, and stability with respect to time, pH, and salinity. We report here on the magnetic characterization of ZDS-coated SPIONs and their in vitro and in vivo performance relative to non-specific interactions with HeLa cells and in mice, respectively. ZDS-coated SPIONs retained the superparamagnetism and saturation magnetization (M(s)) of as-synthesized hydrophobic SPIONs, with M(s) = 74 emu g(-1) [Fe]. Moreover, ZDS-coated SPIONs showed only small non-specific uptake into HeLa cancer cells in vitro and low non-specific binding to serum proteins in vivo in mice.
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Affiliation(s)
- He Wei
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Oliver T. Bruns
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Ou Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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120
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Arias DH, Stone KW, Vlaming SM, Walker BJ, Bawendi MG, Silbey RJ, Bulović V, Nelson KA. Thermally-Limited Exciton Delocalization in Superradiant Molecular Aggregates. J Phys Chem B 2012. [DOI: 10.1021/jp3086717] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Dylan H. Arias
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Katherine W. Stone
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Sebastiaan M. Vlaming
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Brian J. Walker
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Moungi G. Bawendi
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Robert J. Silbey
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Vladimir Bulović
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
| | - Keith A. Nelson
- Department
of Chemistry and Center for Excitonics and ‡Research Laboratory of Electronics
and Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
United States
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121
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Lee J, Sharei A, Sim WY, Adamo A, Langer R, Jensen KF, Bawendi MG. Nonendocytic delivery of functional engineered nanoparticles into the cytoplasm of live cells using a novel, high-throughput microfluidic device. Nano Lett 2012; 12:6322-7. [PMID: 23145796 PMCID: PMC3521073 DOI: 10.1021/nl303421h] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The ability to straightforwardly deliver engineered nanoparticles into the cell cytosol with high viability will vastly expand the range of biological applications. Nanoparticles could potentially be used as delivery vehicles or as fluorescent sensors to probe the cell. In particular, quantum dots (QDs) may be used to illuminate cytosolic proteins for long-term microscopy studies. Whereas recent advances have been successful in specifically labeling proteins with QDs on the cell membrane, cytosolic delivery of QDs into live cells has remained challenging. In this report, we demonstrate high throughput delivery of QDs into live cell cytoplasm using an uncomplicated microfluidic device while maintaining cell viabilities of 80-90%. We verify that the nanoparticle surface interacts with the cytosolic environment and that the QDs remain nonaggregated so that single QDs can be observed.
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Affiliation(s)
- Jungmin Lee
- Department of Chemistry, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Armon Sharei
- Department of Chemical Engineering, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Woo Young Sim
- Department of Chemical Engineering, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Andrea Adamo
- Department of Chemical Engineering, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Robert Langer
- Department of Chemical Engineering, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Klavs F. Jensen
- Department of Chemical Engineering, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
| | - Moungi G. Bawendi
- Department of Chemistry, 77 Massachusetts Avenue, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 USA
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122
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Abstract
The synthesis of III-V quantum dots has been long known to be more challenging than the synthesis of other types of inorganic quantum dots. This is attributed to highly reactive group-V precursors. We synthesized molecules that are suitable for use as group-V precursors and characterized their reactivity using multiple complementary techniques. We show that the size distribution of indium arsenide quantum dots indeed improves with decreased precursor reactivity.
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Affiliation(s)
- Daniel K Harris
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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123
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Kay ER, Lee J, Nocera DG, Bawendi MG. Conformational Control of Energy Transfer: A Mechanism for Biocompatible Nanocrystal-Based Sensors. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201207181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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124
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Jadhav PJ, Brown PR, Thompson N, Wunsch B, Mohanty A, Yost SR, Hontz E, Van Voorhis T, Bawendi MG, Bulović V, Baldo MA. Triplet exciton dissociation in singlet exciton fission photovoltaics. Adv Mater 2012; 24:6169-6174. [PMID: 22968762 DOI: 10.1002/adma.201202397] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 07/23/2012] [Indexed: 06/01/2023]
Abstract
Triplet exciton dissociation in singlet exciton fission devices with three classes of acceptors are characterized: fullerenes, perylene diimides, and PbS and PbSe colloidal nanocrystals. Using photocurrent spectroscopy and a magnetic field probe it is found that colloidal PbSe nanocrystals are the most promising acceptors, capable of efficient triplet exciton dissociation and long wavelength absorption.
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Affiliation(s)
- Priya J Jadhav
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
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125
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Somers RC, Snee PT, Bawendi MG, Nocera DG. Energy Transfer of CdSe/ZnS Nanocrystals Encapsulated with Rhodamine-Dye Functionalized Poly(acrylic acid). J Photochem Photobiol A Chem 2012; 248:24-29. [PMID: 24926175 DOI: 10.1016/j.jphotochem.2012.07.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Energy transfer between a CdSe/ZnS nanocrystal (NC) donor and a rhodamine isothiocyanate (RITC) acceptor has been achieved via a functionalized poly(acrylic acid) (PAA) encapsulating layer over the surface of the NC. The modification of PAA with both N-octylamine (OA) and 5-amino-1-pentanol (AP), [PAA-OA-AP], allows for the simultaneous water-solubilization and functionalization of the NCs, underscoring the ease of synthesizing NC-acceptor conjugates with this strategy. Photophysical studies of the NC-RITC constructs showed that energy transfer is efficient, with kFRET approaching 108 s-1. The ease of the covalent conjugation of molecules to NCs with PAA-OA-AP coating, together with efficient energy transfer, makes the NCs encapsulated with PAA-OA-AP attractive candidates for sensing applications.
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Affiliation(s)
- Rebecca C Somers
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307
| | - Preston T Snee
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, MC 111, Chicago IL, 60607
| | - Moungi G Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307
| | - Daniel G Nocera
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307
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126
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Zhao J, Chen O, Strasfeld DB, Bawendi MG. Biexciton quantum yield heterogeneities in single CdSe (CdS) core (shell) nanocrystals and its correlation to exciton blinking. Nano Lett 2012; 12:4477-83. [PMID: 22871126 PMCID: PMC3482465 DOI: 10.1021/nl3013727] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We explore biexciton (BX) nonradiative recombination processes in single semiconductor nanocrystals (NCs) using confocal fluorescence microscopy and second-order photon intensity correlation. More specifically, we measure the photoluminescence blinking and BX quantum yields (QYs) and study the correlation between these two measurements for single core (shell) CdSe (CdS) nanocrystals (NCs). We find that NCs with a high "on" time fraction are significantly more likely to have a high BX QY than NCs with a low "on" fraction, even though the BX QYs of NCs with a high "on" fraction vary dramatically. The BX QYs of single NCs are also weakly dependent upon excitation wavelength. The weak correlation between exciton "on" fractions and BX QYs suggests that multiple recombination processes are involved in the BX recombination. To explain our results, we propose a model that combines both trapping and an Auger mechanism for BX recombination.
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127
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Mentzel TS, Wanger DD, Ray N, Walker BJ, Strasfeld D, Bawendi MG, Kastner MA. Nanopatterned electrically conductive films of semiconductor nanocrystals. Nano Lett 2012; 12:4404-8. [PMID: 22784104 DOI: 10.1021/nl3022863] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present the first semiconductor nanocrystal films of nanoscale dimensions that are electrically conductive and crack-free. These films make it possible to study the electrical properties intrinsic to the nanocrystals unimpeded by defects such as cracking and clustering that typically exist in larger-scale films. We find that the electrical conductivity of the nanoscale films is 180 times higher than that of drop-cast, microscopic films made of the same type of nanocrystal. Our technique for forming the nanoscale films is based on electron-beam lithography and a lift-off process. The patterns have dimensions as small as 30 nm and are positioned on a surface with 30 nm precision. The method is flexible in the choice of nanocrystal core-shell materials and ligands. We demonstrate patterns with PbS, PbSe, and CdSe cores and Zn(0.5)Cd(0.5)Se-Zn(0.5)Cd(0.5)S core-shell nanocrystals with a variety of ligands. We achieve unprecedented versatility in integrating semiconductor nanocrystal films into device structures both for studying the intrinsic electrical properties of the nanocrystals and for nanoscale optoelectronic applications.
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Affiliation(s)
- Tamar S Mentzel
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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128
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Correa RE, Dauler EA, Nair G, Pan SH, Rosenberg D, Kerman AJ, Molnar RJ, Hu X, Marsili F, Anant V, Berggren KK, Bawendi MG. Single photon counting from individual nanocrystals in the infrared. Nano Lett 2012; 12:2953-2958. [PMID: 22624846 DOI: 10.1021/nl300642k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Experimental restrictions imposed on the collection and detection of shortwave-infrared photons (SWIR) have impeded single molecule work on a large class of materials whose optical activity lies in the SWIR. Here we report the successful observation of room-temperature single nanocrystal photoluminescence at SWIR wavelengths using a highly efficient multielement superconducting nanowire single photon detector. We confirm that the photoluminescence from single lead sulfide nanocrystals is strongly antibunched, demonstrating the feasibility of performing sophisticated photon correlation experiments on individual weak SWIR emitters, and, more broadly, paving the way for sensitive measurements of spectral observables on infrared quantum systems that are incompatible with current detection techniques.
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Affiliation(s)
- Raoul E Correa
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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129
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Osedach TP, Zhao N, Andrew TL, Brown PR, Wanger DD, Strasfeld DB, Chang LY, Bawendi MG, Bulović V. Bias-stress effect in 1,2-ethanedithiol-treated PbS quantum dot field-effect transistors. ACS Nano 2012; 6:3121-7. [PMID: 22480161 DOI: 10.1021/nn3008788] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We investigate the bias-stress effect in field-effect transistors (FETs) consisting of 1,2-ethanedithiol-treated PbS quantum dot (QD) films as charge transport layers in a top-gated configuration. The FETs exhibit ambipolar operation with typical mobilities on the order of μ(e) = 8 × 10(-3) cm(2) V(-1) s(-1) in n-channel operation and μ(h) = 1 × 10(-3) cm(2) V(-1) s(-1) in p-channel operation. When the FET is turned on in n-channel or p-channel mode, the established drain-source current rapidly decreases from its initial magnitude in a stretched exponential decay, manifesting the bias-stress effect. The choice of dielectric is found to have little effect on the characteristics of this bias-stress effect, leading us to conclude that the associated charge-trapping process originates within the QD film itself. Measurements of bias-stress-induced time-dependent decays in the drain-source current (I(DS)) are well fit to stretched exponential functions, and the time constants of these decays in n-channel and p-channel operation are found to follow thermally activated (Arrhenius) behavior. Measurements as a function of QD size reveal that the stressing process in n-channel operation is faster for QDs of a smaller diameter while stress in p-channel operation is found to be relatively invariant to QD size. Our results are consistent with a mechanism in which field-induced nanoscale morphological changes within the QD film result in screening of the applied gate field. This phenomenon is entirely recoverable, which allows us to repeatedly observe bias stress and recovery characteristics on the same device. This work elucidates aspects of charge transport in chemically treated lead chalcogenide QD films and is of relevance to ongoing investigations toward employing these films in optoelectronic devices.
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Affiliation(s)
- Timothy P Osedach
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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130
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Gdor I, Sachs H, Roitblat A, Strasfeld DB, Bawendi MG, Ruhman S. Exploring exciton relaxation and multiexciton generation in PbSe nanocrystals using hyperspectral near-IR probing. ACS Nano 2012; 6:3269-3277. [PMID: 22390473 DOI: 10.1021/nn300184n] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Hyperspectral femtosecond transient absorption spectroscopy is employed to record exciton relaxation and recombination in colloidal lead selenide (PbSe) nanocrystals in unprecedented detail. Results obtained with different pump wavelengths and fluences are scrutinized with regard to three issues: (1) early subpicosecond spectral features due to "hot" excitons are analyzed in terms of suggested underlying mechanisms; (2) global kinetic analysis facilitates separation of the transient difference spectra into single, double, and triple exciton state contributions, from which individual band assignments can be tested; and (3) the transient spectra are screened for signatures of multiexciton generation (MEG) by comparing experiments with excitation pulses both below and well above the theoretical threshold for multiplication. For the latter, a recently devised ultrafast pump-probe spectroscopic approach is employed. Scaling sample concentrations and pump pulse intensities inversely with the extinction coefficient at each excitation wavelength overcomes ambiguities due to direct multiphoton excitation, uncertainties of absolute absorption cross sections, and low signal levels. As observed in a recent application of this method to InAs core/shell/shell nanodots, no sign of MEG was detected in this sample up to photon energy 3.7 times the band gap. Accordingly, numerous reports of efficient MEG in other samples of PbSe suggest that the efficiency of this process varies from sample to sample and depends on factors yet to be determined.
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Affiliation(s)
- Itay Gdor
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel
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131
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Chauhan VP, Stylianopoulos T, Martin JD, Popović Z, Chen O, Kamoun WS, Bawendi MG, Fukumura D, Jain RK. Normalization of tumour blood vessels improves the delivery of nanomedicines in a size-dependent manner. Nat Nanotechnol 2012; 7:383-8. [PMID: 22484912 PMCID: PMC3370066 DOI: 10.1038/nnano.2012.45] [Citation(s) in RCA: 784] [Impact Index Per Article: 65.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 03/12/2012] [Indexed: 05/15/2023]
Abstract
The blood vessels of cancerous tumours are leaky and poorly organized. This can increase the interstitial fluid pressure inside tumours and reduce blood supply to them, which impairs drug delivery. Anti-angiogenic therapies--which 'normalize' the abnormal blood vessels in tumours by making them less leaky--have been shown to improve the delivery and effectiveness of chemotherapeutics with low molecular weights, but it remains unclear whether normalizing tumour vessels can improve the delivery of nanomedicines. Here, we show that repairing the abnormal vessels in mammary tumours, by blocking vascular endothelial growth factor receptor-2, improves the delivery of smaller nanoparticles (diameter, 12 nm) while hindering the delivery of larger nanoparticles (diameter, 125 nm). Using a mathematical model, we show that reducing the sizes of pores in the walls of vessels through normalization decreases the interstitial fluid pressure in tumours, thus allowing small nanoparticles to enter them more rapidly. However, increased steric and hydrodynamic hindrances, also associated with smaller pores, make it more difficult for large nanoparticles to enter tumours. Our results further suggest that smaller (∼12 nm) nanomedicines are ideal for cancer therapy due to their superior tumour penetration.
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Affiliation(s)
- Vikash P Chauhan
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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132
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Mito JK, Ferrer JM, Brigman BE, Lee CL, Dodd RD, Eward WC, Marshall LF, Cuneo KC, Carter JE, Ramasunder S, Kim Y, Lee WD, Griffith LG, Bawendi MG, Kirsch DG. Intraoperative detection and removal of microscopic residual sarcoma using wide-field imaging. Cancer 2012; 118:5320-30. [PMID: 22437667 PMCID: PMC3532657 DOI: 10.1002/cncr.27458] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 12/05/2011] [Accepted: 01/17/2012] [Indexed: 11/17/2022]
Abstract
BACKGROUND: The goal of limb-sparing surgery for a soft tissue sarcoma of the extremity is to remove all malignant cells while preserving limb function. After initial surgery, microscopic residual disease in the tumor bed will cause a local recurrence in approximately 33% of patients with sarcoma. To help identify these patients, the authors developed an in vivo imaging system to investigate the suitability of molecular imaging for intraoperative visualization. METHODS: A primary mouse model of soft tissue sarcoma and a wide field-of-view imaging device were used to investigate a series of exogenously administered, near-infrared (NIR) fluorescent probes activated by cathepsin proteases for real-time intraoperative imaging. RESULTS: The authors demonstrated that exogenously administered cathepsin-activated probes can be used for image-guided surgery to identify microscopic residual NIR fluorescence in the tumor beds of mice. The presence of residual NIR fluorescence was correlated with microscopic residual sarcoma and local recurrence. The removal of residual NIR fluorescence improved local control. CONCLUSIONS: The authors concluded that their technique has the potential to be used for intraoperative image-guided surgery to identify microscopic residual disease in patients with cancer. Cancer 2012. © 2012 American Cancer Society.
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Affiliation(s)
- Jeffrey K Mito
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27708, USA
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133
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Abstract
We fabricated planar PbS quantum dot devices with ohmic and Schottky type electrodes and characterized them using scanning photocurrent and photovoltage microscopies. The microscopy techniques used in this investigation allow for interrogation of the lateral depletion width and related photovoltaic properties in the planar Schottky type contacts. Titanium/QD contacts exhibited depletion widths that varied over a wide range as a function of bias voltage, while the gold/QD contacts showed ohmic behavior over the same voltage range.
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Affiliation(s)
- David B Strasfeld
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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134
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Akselrod GM, Walker BJ, Tisdale WA, Bawendi MG, Bulovic V. Twenty-fold enhancement of molecular fluorescence by coupling to a J-aggregate critically coupled resonator. ACS Nano 2012; 6:467-471. [PMID: 22122758 DOI: 10.1021/nn203789t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report a 20-fold enhancement in the fluorescence of the organic dye DCM when resonantly coupled to a strongly optically absorbing structure of a thin film of spin-deposited molecular J-aggregates in a critically coupled resonator (JCCR) geometry. A submonolayer equivalent of DCM molecules is shown to absorb and re-emit 2.2% of the incident resonant photons when coupled to the JCCR enhancement structure, compared to 0.1% for the bare film of same thickness on quartz. Such a JCCR structure is a general energy focusing platform that localizes over 90% of incident light energy within a 15 nm thin film layer in the form of excitons that can subsequently be transferred to colocated lumophores. Applications of the exciton-mediated concentration of optical energy are discussed in the context of solid-state lighting, photodetection, and single photon optics.
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Affiliation(s)
- Gleb M Akselrod
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 13-3146, Cambridge, Massachusetts 02139, USA.
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135
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Abstract
The potential of superparamagnetic iron oxide nanoparticles (SPIONs) in various biomedical applications, including magnetic resonance imaging (MRI), sensing, and drug delivery, requires that their surface be derivatized to be hydrophilic and biocompatible. We report here the design and synthesis of a compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand with strong binding affinity to SPIONs. After ligand exchange, the ZDS-coated SPIONs exhibit small hydrodynamic diameters, and stability with respect to time, pH, and salinity. Furthermore, small ZDS coated SPIONs were found to have a reduced nonspecific affinity (compared to negatively charged SPIONs) toward serum proteins; streptavidin/dye functionalized SPIONs were bioactive and thus specifically targeted biotin receptors.
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136
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Somers RC, Lanning RM, Snee PT, Greytak AB, Jain RK, Bawendi MG, Nocera DG. A Nanocrystal-based Ratiometric pH Sensor for Natural pH Ranges. Chem Sci 2012; 3:2980-2985. [PMID: 26413260 PMCID: PMC4582792 DOI: 10.1039/c2sc20212c] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A ratiometric fluorescent pH sensor based on CdSe/CdZnS nanocrystal quantum dots (NCs) has been designed for biological pH ranges. The construct is formed from the conjugation of a pH dye (SNARF) to NCs coated with a poly(amido amine) (PAMAM) dendrimer. The sensor exhibits a well-resolved ratio response at pH values between 6 and 8 under linear or two-photon excitation, and in the presence of a 4% bovine serum albumin (BSA) solution.
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Affiliation(s)
- Rebecca C. Somers
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307, USA
| | - Ryan M. Lanning
- Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, MA 02114, USA
| | | | | | - Rakesh K. Jain
- Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, MA 02114, USA
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307, USA
| | - Daniel G. Nocera
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307, USA
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137
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Greytak AB, Allen PM, Liu W, Zhao J, Young ER, Popović Z, Walker B, Nocera DG, Bawendi MG. Alternating layer addition approach to CdSe/CdS core/shell quantum dots with near-unity quantum yield and high on-time fractions. Chem Sci 2012; 3:2028-2034. [PMID: 24932403 DOI: 10.1039/c2sc00561a] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report single-particle photoluminescence (PL) intermittency (blinking) with high on-time fractions in colloidal CdSe quantum dots (QD) with conformal CdS shells of 1.4 nm thickness, equivalent to approximately 4 CdS monolayers. All QDs observed displayed on-time fractions > 60% with the majority > 80%. The high-on-time-fraction blinking is accompanied by fluorescence quantum yields (QY) close to unity (up to 98% in an absolute QY measurement) when dispersed in organic solvents and a monoexponential ensemble photoluminescence (PL) decay lifetime. The CdS shell is formed in high synthetic yield using a modified selective ion layer adsorption and reaction (SILAR) technique that employs a silylated sulfur precursor. The CdS shell provides sufficient chemical and electronic passivation of the QD excited state to permit water solubilization with greater than 60% QY via ligand exchange with an imidazole-bearing hydrophilic polymer.
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Affiliation(s)
- Andrew B Greytak
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Peter M Allen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Wenhao Liu
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Jing Zhao
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Elizabeth R Young
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Zoran Popović
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Brian Walker
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Daniel G Nocera
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
| | - Moungi G Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts, USA
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138
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Abstract
Synthetic methods yielding highly uniform colloidal semiconductor nanocrystals with controlled shapes and sizes are now available for many materials. These methods have enabled geometrical control of optical properties, which are difficult or impossible to achieve in conventional bulk solids. However, incorporating nanocrystals efficiently into photodetectors remains challenging because of the low charge carrier mobilities typical of nanocrystal solids. Here we present an approach based on exciton energy transfer from CdSe/CdS core/shell nanocrystals to embedded CdSe nanowires. By combining the wide electronic tunability of nanocrystals with the excellent one-dimensional charge transport characteristics obtainable in nanowires, we are able to increase photocurrent extraction from a nanocrystal solid by 2-3 orders of magnitude. Furthermore, we correlate local device morphology with optoelectronic functionality by measuring the local photocurrent response in a scanning confocal microscope. We also discuss how nancocrystal/nanowire hybrid devices could be used in particle detector systems.
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Affiliation(s)
- August Dorn
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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139
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Chauhan VP, Popović Z, Chen O, Cui J, Fukumura D, Bawendi MG, Jain RK. Fluorescent Nanorods and Nanospheres for Real-Time In Vivo Probing of Nanoparticle Shape-Dependent Tumor Penetration. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201104449] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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140
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Chauhan VP, Popović Z, Chen O, Cui J, Fukumura D, Bawendi MG, Jain RK. Fluorescent nanorods and nanospheres for real-time in vivo probing of nanoparticle shape-dependent tumor penetration. Angew Chem Int Ed Engl 2011; 50:11417-20. [PMID: 22113800 DOI: 10.1002/anie.201104449] [Citation(s) in RCA: 308] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 08/16/2011] [Indexed: 11/12/2022]
Affiliation(s)
- Vikash P Chauhan
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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141
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Geyer SM, Scherer JM, Moloto N, Jaworski FB, Bawendi MG. Efficient luminescent down-shifting detectors based on colloidal quantum dots for dual-band detection applications. ACS Nano 2011; 5:5566-5571. [PMID: 21591692 DOI: 10.1021/nn2010238] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A colloidal quantum dot (QD) luminescent down-shifting (LDS) layer is used to sensitize an InGaAs short wavelength infrared photodetector to the near UV spectral band. An average improvement in the external quantum efficiency (EQE) from 1.8% to 21% across the near UV is realized using an LDS layer consisting of PbS/CdS core/shell QDs embedded in PMMA. A simple model is used to fit the experimental EQE data. A UV sensitive InGaAs imaging array is demonstrated and the effect of the LDS layer on the optical resolution is calculated. The bandwidth of the LDS detector under UV illumination is characterized and shown to be determined by the photoluminescence lifetime of the QDs.
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Affiliation(s)
- Scott M Geyer
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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142
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Brown PR, Lunt RR, Zhao N, Osedach TP, Wanger DD, Chang LY, Bawendi MG, Bulović V. Improved current extraction from ZnO/PbS quantum dot heterojunction photovoltaics using a MoO3 interfacial layer. Nano Lett 2011; 11:2955-61. [PMID: 21661734 DOI: 10.1021/nl201472u] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The ability to engineer interfacial energy offsets in photovoltaic devices is one of the keys to their optimization. Here, we demonstrate that improvements in power conversion efficiency may be attained for ZnO/PbS heterojunction quantum dot photovoltaics through the incorporation of a MoO(3) interlayer between the PbS colloidal quantum dot film and the top-contact anode. Through a combination of current-voltage characterization, circuit modeling, Mott-Schottky analysis, and external quantum efficiency measurements performed with bottom- and top-illumination, these enhancements are shown to stem from the elimination of a reverse-bias Schottky diode present at the PbS/anode interface. The incorporation of the high-work-function MoO(3) layer pins the Fermi level of the top contact, effectively decoupling the device performance from the work function of the anode and resulting in a high open-circuit voltage (0.59 ± 0.01 V) for a range of different anode materials. Corresponding increases in short-circuit current and fill factor enable 1.5-fold, 2.3-fold, and 4.5-fold enhancements in photovoltaic device efficiency for gold, silver, and ITO anodes, respectively, and result in a power conversion efficiency of 3.5 ± 0.4% for a device employing a gold anode.
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Affiliation(s)
- Patrick R Brown
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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143
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Wood V, Panzer MJ, Bozyigit D, Shirasaki Y, Rousseau I, Geyer S, Bawendi MG, Bulović V. Electroluminescence from nanoscale materials via field-driven ionization. Nano Lett 2011; 11:2927-2932. [PMID: 21678932 DOI: 10.1021/nl2013983] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The high degree of morphological and energetic disorder inherent to many nanosized materials places limitations on charge injection into and transport rates through thin films of these materials. We demonstrate electroluminescence achieved by local generation of charge that eliminates the need for injection of charge carriers from the device electrodes. We show electroluminescence from thin films of nanoscale materials that do not support direct current excitation and suggest a mechanism for the charge generation and electroluminescence that is consistent with our time-averaged and time-resolved observations.
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Affiliation(s)
- Vanessa Wood
- Department of Information Technology and Electrical Engineering ETH Zurich, 35 Gloriastrasse, 8092 Zurich Switzerland
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144
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Walker BJ, Dorn A, Bulović V, Bawendi MG. Color-selective photocurrent enhancement in coupled J-aggregate/nanowires formed in solution. Nano Lett 2011; 11:2655-2659. [PMID: 21615089 DOI: 10.1021/nl200679n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
J-aggregates are ordered clusters of coherently coupled molecular dyes, (1) and they have been used as light sensitizers in film photography due to their intense absorptions. Hybrid structures containing J-aggregates may also have applications in devices that require spectral specificity, such as color imaging or optical signaling. (2) However the use of J-aggregates in optoelectronic devices has posed a long-standing challenge (3, 4) due to the difficulty of controlling aggregate formation and the low charge carrier mobility of many J-aggregates in solid state. In this paper, we demonstrate a modular method to assemble three different cyanine J-aggregates onto CdSe nanowires, resulting in a photodetector that is color-sensitized in three specific, narrow absorption bands. Both the J-aggregate and nanowire device components are fabricated from solution and the sensitizing wavelength is switched from blue to red to green, using only solution-phase exchange of the J-aggregates on the same underlying device.
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Affiliation(s)
- Brian J Walker
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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145
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Nair G, Chang LY, Geyer SM, Bawendi MG. Perspective on the prospects of a carrier multiplication nanocrystal solar cell. Nano Lett 2011; 11:2145-51. [PMID: 21500807 DOI: 10.1021/nl200798x] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This article presents a perspective on the experimental and theoretical work to date on the efficiency of carrier multiplication (CM) in colloidal semiconductor nanocrystals (NCs). Early reports on CM in NCs suggested large CM efficiency enhancements. However, recent experiments have shown that CM in nanocrystalline samples is not significantly stronger, and often is weaker, than in the parent bulk when compared on an absolute photon energy basis. This finding is supported by theoretical consideration of the CM process and the competing intraband relaxation. We discuss the experimental artifacts that may have led to the apparently strong CM estimated in early reports. The finding of bulklike CM in NCs suggests that the main promise of quantum confinement is to boost the photovoltage at which carriers can be extracted. With this in mind, we discuss research directions that may result in effective use of CM in a solar cell.
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Affiliation(s)
- Gautham Nair
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02143, United States
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146
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Abstract
Biexciton properties strongly affect the usability of a light emitter in quantum photon sources and lasers but are difficult to measure for single fluorophores at room temperature due to luminescence intermittency and bleaching at the high excitation fluences usually required. Here, we observe the biexciton (BX) to exciton (X) to ground photoluminescence cascade of single colloidal semiconductor nanocrystals (NCs) under weak excitation in a g((2)) photon correlation measurement and show that the normalized amplitude of the cascade feature is equal to the ratio of the BX to X fluorescence quantum yields. This imposes a limit on the attainable depth of photon antibunching and provides a robust means to study single emitter biexciton physics. In NC samples, we show that the BX quantum yield is considerably inhomogeneous, consistent with the defect sensitivity expected of the Auger nonradiative recombination mechanism. The method can be extended to study X,BX spectral and polarization correlations.
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Affiliation(s)
- Gautham Nair
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Jing Zhao
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Moungi G Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
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147
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Harris DK, Allen PM, Han HS, Walker BJ, Lee J, Bawendi MG. Synthesis of Cadmium Arsenide Quantum Dots Luminescent in the Infrared. J Am Chem Soc 2011; 133:4676-9. [DOI: 10.1021/ja1101932] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniel K. Harris
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Peter M. Allen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Hee-Sun Han
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Brian J. Walker
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Jungmin Lee
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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148
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Popović Z, Liu W, Chauhan VP, Lee J, Wong C, Greytak AB, Insin N, Nocera DG, Fukumura D, Jain RK, Bawendi MG. A nanoparticle size series for in vivo fluorescence imaging. Angew Chem Int Ed Engl 2011; 49:8649-52. [PMID: 20886481 DOI: 10.1002/anie.201003142] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Zoran Popović
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139-4307, USA
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149
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Abstract
ABSTRACTWe present a synthesis of colloidal CdTe nanocrystals whose absolute room temperature quantum yields are routinely above 60%. The preparation is based on the trioctylphosphine oxide (TOPO) method reported by Murray, with a more stalbe tellurium precursor now used as the chalcogenide source. The photoluminescence is continuously tunable over the range 590-760 nm and is as narrow as 135 meV (45 nm) FWHM. No deep trap luminescence is detected for the diameter range 4-11 nm. CdTe nanocrystals are characterized by UV/vis absorption, photoluminescence emission, transmission electron microscopy, and powder X-ray diffraction.
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150
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Geyer SM, Allen PM, Chang LY, Wong CR, Osedach TP, Zhao N, Bulovic V, Bawendi MG. Control of the carrier type in InAs nanocrystal films by predeposition incorporation of Cd. ACS Nano 2010; 4:7373-7378. [PMID: 21126000 DOI: 10.1021/nn101772n] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nanocrystal (NC) films have been proposed as an alternative to bulk semiconductors for electronic applications such as solar cells and photodetectors. One outstanding challenge in NC electronics is to robustly control the carrier type to create stable p-n homojunction-based devices. We demonstrate that the postsynthetic addition of Cd to InAs nanocrystals switches the resulting InAs:Cd NC films from n-type to p-type when operating in a field effect transistor. This method presents a stable, facile way to control the carrier type of InAs nanocrystals prior to deposition. We present two mechanisms to explain the observed switch in carrier type. In mechanism 1, Cd atoms are incorporated at In sites in the lattice and act as acceptor defects, forming a partially compensated p-type semiconductor. In mechanism 2, Cd atoms passivate donor-type InAs surface states and create acceptor-type surface states. This work represents a critical step toward the creation of p-n homojunction-based NC electronics.
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Affiliation(s)
- Scott M Geyer
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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